Two Mars Orbiters Chatted For Atmospheric Science

Mission extensions for interplanetary robot explorers are usually continuations of their primary mission. But sometimes the hardware already on board are put to novel uses. European Space Agency has started using radio equipment on board two Mars orbiters to probe the Martian atmosphere.

The scientific basis is straightforward: radio signals are affected by whatever they had traveled through. When transmitting data, such effects are noises to be minimized. But we can also leverage it for atmospheric science here on Earth. ESA applied the same concept at Mars: by transmitting a known signal from one Mars orbiter to another, changes in the received signal tells scientists something about the Martian atmosphere between them.

So the theory sounds good, but the engineering implementation took some work. Most radio equipment on board ESA’s orbiters were not designed to talk to each other. In fact they were deliberately different to minimize interference. However, both Mars Express and Trace Gas Orbiter were designed to act as data relays for surface probes, and not just the one they each carried to Mars. Thus their related radio gear were flexible enough to be adapted to this experiment.

These two machines launched over a decade apart. Yet they could now communicate with each other in Mars orbit using radios originally designed for talking to the surface. In the near future such chatter will probably be limited, as Trace Gas Orbiter is still in the middle of its primary mission. But this success lets ESA think about how much further to push the idea in the future. In the meantime Mars Express will continue its observation of Mars, doing things like giving us context on Perseverance rover landing.

9 thoughts on “Two Mars Orbiters Chatted For Atmospheric Science

  1. It won’t be that long really and the Martian version of Starlink will be on it’s way to provide all of Mars with a High-Bandwidth global communication network. The exploration of Mars will really start to heat up when scientists can beam back large quantities of data a day.

    1. I wouldn’t really compare such an idea to Starlink because Starlink is obscenely complicated for very different requirements.

      It makes a lot more sense to put a handful of satellites in aressynchronous orbit and have four aresstationary signal relay satellites. This radically reduces the requirements for communicating since the rovers, base stations, etc. don’t have to bother with satellite tracking or signal distortion as a satellite moves.

  2. The Voyager probe used this method to probe the atmosphere of planets it was passing. When the probe’s signal was to pass through the planets atmosphere, the probe would transmit a constant unmodulated signal. Variations in its phase were measured on earth and these measurements were used to infer what the planet’s atmosphere was like. As I recall, this method was added on later to the mission and proved successful.

    1. Indeed! This was mentioned in the linked article. The problem is that signals received by DSN antennas has been affected by Earth atmosphere as well.

      By using two Mars probes, we can be certain all effects are due to Mars atmosphere alone.

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